It has previously been proposed to provide transverse perforations in a folding apparatus, in which the perforations are applied in advance of the folding of a sheet. A folding blade or knife is formed with perforation teeth. A collection cylinder is provided, having a counter roller with a perforating groove. The structure requires an additional counter roller which requires space and is costly to install. Perforating is possible only at the actual fold or crease line of the first transfer fold.